Copper contamination detection method and system for monitoring copper contamination

ABSTRACT

A method of monitoring copper contamination. The method includes method, comprising: (a) ion-implanting an N-type dopant into a region of single-crystal silicon substrate, the region abutting a top surface of the substrate; (c) activating the N-type dopant by annealing the substrate at a temperature of 500° C. or higher in an inert atmosphere; (c) submerging, for a present duration of time, the substrate into an aqueous solution, the aqueous solution to be monitored for copper contamination; and (d) determining an amount of copper adsorbed from the aqueous solution by the region of the substrate.

RELATED APPLICATIONS

This Application is related to application Ser. No. 11/863,623 filed onSep. 28, 2007 entitled “COPPER CONTAMINATION DETECTION METHOD AND SYSTEMFOR MONITORING COPPER CONTAMINATION”.

FIELD OF THE INVENTION

The present invention relates to the field of integrated circuitfabrication; more specifically, it relates to a method for monitoringcopper contamination in an integrated circuit fabrication facility and asystem for monitoring copper contamination in an integrated circuitfabrication facility.

BACKGROUND OF THE INVENTION

Modern integrated circuits are fabricated with copper interconnectionwiring. Wet processing tanks in the integrated circuit fabrication canbe contaminated with copper, causing yield loss and reliabilityconcerns. Accordingly, there exists a need in the art for methods andsystems for monitoring copper contamination of solution in wetprocessing tanks in integrated circuit manufacturing facilities.

SUMMARY OF THE INVENTION

A first aspect of the present invention is a method, comprising: (a)ion-implanting an N-type dopant into a region of single-crystal siliconsubstrate, the region abutting a top surface of the substrate; (c)activating the N-type dopant by annealing the substrate at a temperatureof 500° C. or higher in an inert atmosphere; (c) submerging, for apresent duration of time, the substrate into an aqueous solution, theaqueous solution to be monitored for copper contamination; and (d)determining an amount of copper adsorbed from the aqueous solution bythe region of the substrate.

A second aspect of the present invention is the first aspect, furtherincluding: before (a), forming a thermal oxide layer on the top surfaceof the substrate.

A third aspect of the present invention is the second aspect, furtherincluding: between (c) and (d), removing the thermal oxide layer.

A fourth aspect of the present invention is the first aspect, furtherincluding: before (a), cleaning the top surface of the substrate.

A fifth aspect of the present invention is the first aspect, furtherincluding: before (a), selecting an ion implantation N-type dopant doseand energy to repeatably provide a copper measuring sensitivity of theregion of the substrate in the range of copper concentrations expectedto be found in the solution.

A sixth aspect of the present invention is the first aspect, furtherincluding: (e) determining a copper concentration of the solution basedon the amount of copper found in the region of the substrate.

A seventh aspect of the present invention is the sixth aspect, wherein(e) includes: determining the copper concentration of the solution basedon an empirically derived curve, table or formula derived from measuringamounts of copper in monitor wafers submerged, for the present durationof time, in respective aqueous solutions having known and differentcopper concentrations.

An eighth aspect of the present invention is the first aspect, furtherincluding: using the solution in a fabrication process used to fabricateintegrated circuits.

A ninth aspect of the present invention is the first aspect, furtherincluding: containing the solution in a processing tank of a wetprocessing tool used in the fabrication process used to fabricateintegrated circuits.

A tenth aspect of the present invention is the first aspect, wherein thesolution to be monitored in selected from the group consisting ofaqueous wafer cleaning solutions, aqueous wafer etching solutions,aqueous photoresist developing solutions and aqueous photoresist removalsolutions.

An eleventh aspect of the present invention is the first aspect, whereinthe solution to be monitored contains fluorine ions.

A twelfth aspect of the present invention is the first aspect, whereinafter (c), a concentration of the N-type dopant in the region is betweenabout 5 E19 atm/cm³ and about 1 E22 atm/cm³.

A thirteenth aspect of the present invention is the first aspect,wherein the determining the amount of copper in the region of thesubstrate includes performing Total Internal Reflected X-RayFluorescence, Secondary Ion Mass Spectroscopy, Time of Flight SIMS,Energy Dispersive X-Ray Fluorescence, Auger Spectroscopy or X-RayPhoto-electron Spectroscopy.

A fourteenth aspect of the present invention is the first aspect,further including: based on the determining an amount of copper in theregion of the substrate, (e) implementing a corrective action selectedfrom the group consisting of shutting down a tank of a wet processingtool used in the fabrication of integrated circuits containing thesolution, limiting types of product wafers allowed in the tank,restricting fabrication levels of product wafers allowed in the tank,limiting a number of product wafers that can be processed beforeshutting down the tank, and shutting down the tank, draining thesolution from the tank, cleaning the tank, and refilling the tank withfresh solution.

A fifteenth aspect of the present invention is a method, comprising: (a)forming a multiplicity of contamination monitors, each contaminationmonitor comprising an N-type region in a single-crystal siliconsubstrate, the region abutting a top surface of the substrate; (b)selecting an unused contamination monitor of the multiplicity ofcontamination monitors and submerging, for a preset duration of time,the selected contamination monitor of the multiplicity of contaminationmonitors into an aqueous solution contained in a tank of a processingtool used to fabricate integrated circuits; after (b), (c) determiningan amount of copper in the region of the substrate of the onecontamination monitor; after (c), (d) if the amount of copper exceeds apreset limit, taking a corrective action to prevent copper contaminationof the integrated circuits; and (e) repeating steps (b) through (d)periodically.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention are set forth in the appended claims. Theinvention itself, however, will be best understood by reference to thefollowing detailed description of an illustrative embodiment when readin conjunction with the accompanying drawings, wherein:

FIGS. 1A through 1D are cross-sectional drawings illustratingpreparation of a monitor wafer according to embodiments of the presentinvention:

FIG. 2 is a flowchart for testing for copper contamination according toembodiments of the present invention;

FIGS. 3A and 3B are flowcharts illustrating calibration of measurementprocedures according to embodiments of the present invention;

FIG. 4 is a log-log plot of known (or measured) copper concentration ofa solution in a tank versus wafer surface copper concentration of waferssoaked in the solution of the tank;

FIG. 5 is a plot of known copper concentrations of solutions in controltanks versus wafer copper surface concentration by time of soak;

FIG. 6 is a plot of known copper concentration of a solution in acontrol tank versus wafer copper surface concentrations obtained by twowafer measurement techniques at a first dopant level;

FIG. 7 is a plot of known copper concentration of a solution in acontrol tank versus wafer copper surface concentrations obtained by twowafer measurement techniques at a second dopant level; and

FIG. 8 is a schematic block diagram of a general-purpose computer forpracticing the embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Integrated circuits are fabricated in silicon layers of disc shapedsemiconductor substrates often referred to as wafers. These wafers canhave diameters of, to give a few examples, of 125 mm, 200 mm and 300 mm.The fabrication of integrated circuits requires frequent dipping ofwafers into tanks containing various neutral, acidic (e.g.,hydrofluoric, nitric, sulfuric, phosphoric and acetic) and basic(potassium hydroxide, tetramethylammonium hydroxide, ammonium hydroxide)aqueous wafer cleaning solutions, aqueous wafer etching solutions,aqueous photoresist developing solutions and aqueous photoresist removalsolutions. Copper dissolved in these solutions can be adsorbed on thesurface of N-type silicon when the surface concentration of N-typedopant (e.g., arsenic, phosphorous) exceeds a threshold value (e.g.,about 1 E13 atm/cm² or higher). The higher the N-type dopant surfaceconcentration, the more copper will be adsorbed on the surface.

FIGS. 1A through 1D are cross-sectional drawings illustratingpreparation of a monitor wafer according to embodiments of the presentinvention. In FIG. 1A a lightly (having a resistivity between about 10ohm-cm and about 20 ohm-cm P-doped single-crystal silicon substrate 100is provided. Substrate 100 may be cleaned, in one example, by immersionan aqueous solution of ammonia and hydrogen peroxide followed byimmersion an aqueous solution of hydrogen chloride and hydrogenperoxide. Alternatively, substrate 100 may be lightly doped N-type(having a resistivity between about 50 ohm-cm and about 0.7 ohm-cm.Alternatively, substrate 100, may comprise upper and lowersingle-crystal silicon layers separated by a buried oxide (BOX) layer,commonly known as a silicon-on-insulator (SOI) substrate. Substrate 100is advantageously a wafer having the same dimensions (diameter andthickness) of wafers on which integrated circuits processed through thetanks to be monitored. This allows normal wafer handling mechanisms andwafer routing procedures to be used.

In FIG. 1B, an optional thermal silicon dioxide layer 105 is grown on bythermal oxidation (e.g., by oxidation at a temperature of about 500° C.or higher in oxygen in a furnace for about 30 minutes or by oxidation ata temperature of about 900° C. in oxygen for 5 seconds in arapid-thermal-anneal (RTA) tool) of the surfaces of substrate 100. Inone example, silicon dioxide layer is between about 0.4 nm and about 20nm thick. Silicon dioxide layer 105 protects substrate 100 fromcontamination. Silicon dioxide layer 105 also helps to control thedopant profile generated by the steps described infra in relation toFIG. 1C.

In FIG. 1C, an N-type ion implantation 110 is performed followed by anannealing step (e.g., at a temperature of about 500° C. or higher in aninert atmosphere in a furnace for about 30 minutes or at a temperatureof about 900° C. in an inert atmosphere for 5 seconds in a RTA tool) toform an N-doped silicon region 115 in substrate 110. N-type ionimplantation 110 may implant a phosphorus species or an arsenic speciesor a combination of both and arsenic and phosphorus species. N-dopedregion 115 extends from top surface 120 of substrate 100 a depth intothe substrate determined by the thickness of silicon dioxide layer 105,the ion implantation dose, the ion implantation accelerating voltage,the ion implantation species and the anneal time and temperature. In oneexample, the ion implantation accelerating voltage is between about 2KeV and about 25 KeV. In one example, the ion implantation dose ofN-dopant species is between about 4 E13 atm/cm² and about 1 E16 atm/cm².The higher the concentration, the higher the sensitivity of the monitorto copper, but above ion implantation does of about 1 E16 atm/cm² costand time of the ion implantation may be a factor. The dopant ionimplantation dose and energy should be selected to repeatably provide acopper measuring sensitivity in the range of copper concentrationsexpected to be found in the solutions to be monitored.

At this point fabrication of the monitor wafer may be terminated and themonitor wafer stored for future use. Alternatively, the processdescribed infra in reference to FIG. 1D may be performed.

In FIG. 1D, thermal oxide layer 105 (see FIG. 1C) is removed. In oneexample, by etching in an aqueous hydrofluoric acid solution followed bya water rinse. The hydrofluoric acid solution may include ethyleneglycol or ammonium fluoride. Other SiO₂ etchants may be used. A verythin native oxide layer (about 0.1 nm or less will form after rinsing).At this point the wafers may be stored. If no silicon oxide layer 105was formed, then this step may be eliminated. A post anneal clean,similar to that described supra in reference to FIG. 1A may beperformed.

In the steps of FIGS. 2, 3A and 3B that follow, either a whole monitorwafer may be used or a portion of a monitor wafer. While the method willbe described using whole wafers, it should be understood that wholewafers may be broken into multiple pieces and these pieces used insteadof whole wafers. The use of whole wafers allows the use of the normalwafer handling equipment of automated processing tools. The use ofpieces of monitor wafers reduces the cost preparing monitor wafers.

FIG. 2 is a flowchart for testing for copper contamination according toembodiments of the present invention. The method of monitoring forcopper contamination starts by selecting a monitor wafer prepared asdescribed supra. Step 125 is optional and is performed if the solutionin the tank to be tested will not remove SiO₂ (e.g., does not containfluorine ions) or will remove SiO₂ at such a slow rate as to effect themeasurement or impact manufacturing schedules, then the monitor wafer isprepared by removing the SiO₂ layer (either thermal oxide layer 105 ofFIG. 1C or the native oxide formed after removal of the thermal oxidelayer as described supra). Removal of SiO₂ may be accomplished, forexample, by etching in an aqueous hydrofluoric acid solution followed bya water rinse. The hydrofluoric acid solution may include ethyleneglycol or ammonium fluoride. Other SiO₂ etchants may be used. If thesolution of the tank to be tested will remove SiO₂, then step 125 may beskipped. The SiO₂ is removed because copper ions are not adsorbed onSiO₂ surfaces.

In step 130 the monitor wafer is dipped into the solution of the tank tobe tested for a preset duration of time. After the preset time expires,in step 135, the monitor wafer is removed from the tank, rinsed indeionized water and dried. Then in step 140 the copper content of themonitor wafer is measured.

There are many methods and tools that may be used to measure the coppercontent of thin regions of the surface of the monitor wafer. Examplesinclude, but are not limited to Total Internal Reflected X-RayFluorescence (TXFR), Secondary Ion Mass Spectroscopy (SIMS), Time ofFlight SIMS (TOFSIMS), Energy Dispersive X-Ray Fluorescence (EDX), AugerSpectroscopy and X-Ray Photo-electron Spectroscopy (XPS).

In Step 145, a decision is made to compare the resultant coppermeasurement directly to an amount of copper allowed monitor waferspecification or convert the measurement to a copper concentration(e.g., parts per billion PPB) and compare to a copper concentrationallowed in the solution specification. If conversion to solutionconcentration is required the method proceeds to step 150, otherwise themethod proceeds to step 155.

If the comparison is to be based on a copper in solution concentrationthen in step 150 the measurement obtained in step 145 is converted, forexample by use of a conversion graph (see FIG. 4), a conversion formulaor a look-up table. In reality all three conversion methods areprocedures applied to the same data. It should be understood that thereare two types of copper in solution concentration conversions that canbe performed and which are described infra in relation to FIGS. 3A, 3Band 4.

In step, 155, comparison to a specification indicating either a measuredcopper value or of a converted to copper in solution concentration valueis performed. In one example the comparison is a simple look-up tableprocedure or a calculation based on a conversion formula. In oneexample, this is a control chart procedure, where results of values overtime are charted, various statistical analysis are performed and controllimits applied.

In step, 160, it is determined if the copper specification has beenexceeded. If the copper specification has been exceeded, then the methodproceeds to step 165, otherwise the method proceeds to step 170. In step170, corrective action is taken. Corrective actions can include, forexample, shutting down the tank and changing the solution, limiting thetype of product wafers allowed in a particular tank (e.g., by partnumber), restricting the fabrication level of the product wafers allowedin the tank (e.g., to levels less sensitive or insensitive to coppercontamination), limiting the number of product wafers that can beprocessed before shutting the tank down, and shutting the tank down,draining the contaminated solution, cleaning the tank, and refillingwith fresh solution.

In step 170, the copper measurement and/or converted copper in solutionvalue is labeled by date/time and tank ID and saved, and the method iscomplete.

FIGS. 3A and 3B are flowcharts illustrating calibration of measurementprocedures according to embodiments of the present invention. Referringto FIG. 3A, in step 175 several solutions having known copperconcentrations are prepared. These solutions may contain a fluorinebased etchant. In step 180, the concentration of copper in the varioustest solutions is optionally verified by conventional quantitativecopper analysis techniques. In step 185, monitor wafers are dipped intothe different test solutions for a preset duration of time. The samepreset duration of time is used for each solution. A different monitorwafer is dipped into each test solution. After rinsing and drying, thecopper concentrations of the monitor wafers are measured using theanalysis technique described in step 140 of FIG. 2 (e.g., TXFR, etc). Instep 190, the copper concentrations measured in step 185 are plottedversus the copper concentrations from step 175 or 180 (see curve 225 ofFIG. 4). The data points obtained may also be entered into a databaseand a conversion formula calculated from the data points.

Referring to FIG. 3B, step 195 the copper concentrations of a solutionin a production tank is measured by conventional quantitative copperanalysis techniques. In step 200, monitor wafers are dipped into thesolution of the production tank for the same preset duration of timeused in step 185 of FIG. 3A. After rinsing and drying, the copperconcentrations of the monitor wafer is measured using the analysistechnique used in step 185 of FIG. 3A (e.g., TXFR, etc). In step 205, itis determined if more data point are required. If more data points arerequired, then in step 210 enough time is allowed to pass to ensure asignificant number (e.g., several hundred) production wafers have beenprocessed though the solution of the production tank before proceedingto step 195. Otherwise the method proceeds to step 215. In step 215, thecopper concentrations measured in step 200 are plotted versus the copperconcentrations from step 195 (see curve 220 of FIG. 4). The data pointsobtained may also be entered into a database and a conversion formulacalculated from the data points.

FIG. 4 is a log-log plot of known (or measured) copper concentration ofa solution in a tank versus wafer copper surface concentration of waferssoaked in the solution of the tank. The monitor wafers used to preparecurves 220 and 225 were processed by implanting a dose of 1E16 atm/cm²arsenic at 2 KeV into a P type substrate and then RTA at 900° C. for 5minutes. The sheet resistance was measured at 48 ohm/cm². In FIG. 4,curve 225 is based on test solutions prepared in control tanks and curve225 is based on solutions in production tanks. The wafer concentrationswere obtained using TXFR. From FIG. 4 it can be seen that both curves220 and 225 are linear in a log-log scale. From FIG. 4 it can be seenthat there is a constant offset between curve 220 and curve 225, withcurve 220 (production tank solution) reporting more copper in solutionthan curve 225 (test tank solution) for the same TXRF value. This isthought to occur because of additional chemicals (e.g., dissolved Si) inthe production tank enhancing monitor wafer copper adsorption or adifference in fluorine ion content between the production and testsolutions. The TXFR measurement reports less copper in the productionbath than is actually present. Therefore, step 150 of FIG. 2 can useeither of curve 220 or 225 (or formulas or look-up tables based on thedata points of curves 220 and 225) for conversion.

FIG. 5 is a plot of known copper concentrations of solutions in controltanks versus wafer copper surface concentration by time of soak. Thewafer concentrations were obtained using TXFR. FIG. 5 shows that copperadsorption by the monitor wafers is linear over time over a wide (e.g. 4ppb to 40 ppb) range of copper in solution concentrations. The numberabove each histogram are approximate.

FIG. 6 is a plot of known copper concentration of a solution in acontrol tank versus wafer copper surface concentrations obtained by twowafer measurement techniques at a first dopant level. In FIG. 6,measurements were made on similar monitor wafer using TXRF and TOFSIMS.The monitor wafers used to prepare FIG. 6 were processed by implanting adose of 16 atm/cm² arsenic at 2 KeV into a P type substrate and then RTAat 900° C. for 5 minutes.

FIG. 7 is a plot of known copper concentration of a solution in acontrol tank versus wafer copper surface concentrations obtained by twowafer measurement techniques at a second dopant level. In FIG. 6,measurements were made on similar monitor wafer using TXRF and TOFSIMS.The monitor wafers used to prepare FIG. 6 were processed by implanting adose of 5E15 atm/cm² arsenic at 2 KeV into a P type substrate and thenRTA at 900° C. for 5 minutes.

Comparing FIGS. 6 and 7, the two methods (TXRF and TOFSIMS) generatedifferent values, but track very well.

TXRF reports about the same copper solution concentrations for bothdopant levels, while TOFSIMS reports about the same copper solutionconcentrations for both dopant levels except at 80 ppb and TXRF andTOFSIMS generally track, except for 80 ppb. To ensure the highestaccuracy, calibration should be performed using the same dopant levelmonitor wafers and same wafer copper concentration measurementtechnique.

FIG. 8 is a schematic block diagram of a general-purpose computer forpracticing the embodiments of the present invention. In FIG. 8, computersystem 300 has at least one microprocessor or central processing unit(CPU) 305. CPU 305 is interconnected via a system bus 310 to a dynamicrandom access memory (DRAM) device 315 and a read-only memory (ROM)device 320, an input/output (I/O) adapter 325 for a connecting aremovable data and/or program storage device 330 and a mass data and/orprogram storage device 335, a user interface adapter 330 for connectinga keyboard 335 and a mouse 350, a port adapter 355 for connecting a dataport 360 and a display adapter 365 for connecting a display device 370.

Either of devices 315 and 320 includes contains the basic operatingsystem for computer system 300. Removable data and/or program storagedevice 330 may be a magnetic media such as a floppy drive, a tape driveor a removable hard disk drive or optical media such as CD ROM or adigital video disc (DVD) or solid state memory such as ROM or DRAM orflash memory. Mass data and/or program storage device 335 may be a harddisk drive or an optical drive. In addition to keyboard 335 and mouse350, other user input devices such as trackballs, writing tablets,pressure pads, microphones, light pens and position-sensing screendisplays may be connected to user interface 330. Examples of displaydevices include cathode-ray tubes (CRT) and liquid crystal displays(LCD).

One of devices 315, 320, 330 or 335 includes a computer code 375(illustrated by way of example in device 315), which is a computerprogram that comprises computer-executable instructions. Computer code375 includes an algorithm for generating calibration and conversioncurves, tables or equation for copper in solution to copper adsorbed ona monitor wafer surfaces as well as for monitoring copper contaminationin production wet processing tanks (e.g. the algorithm of FIGS. 2, 3A,3B and curves of FIG. 4). CPU 305 executes computer code 375. Additionalactivities implemented on the computer system 300 include generatinghistory or trend charts from periodic monitor measurements andperforming statistical analysis on the periodic data. Any of devices315, 320, 330 or 335 may include input data 380 (illustrated by way ofexample in device 335) required by computer code 375. Display device 370displays output from computer code 375.

Any or all of devices 315, 320, 330 and 335 (or one or more additionalmemory devices not shown in FIG. 3) may be used as a computer usablemedium (or a computer readable medium or a program storage device)having a computer readable program embodied therein and/or having otherdata stored therein, wherein the computer readable program comprisescomputer code 375. Generally, a computer program product (or,alternatively, an article of manufacture) of the computer system 300 maycomprise the computer usable medium (or the program storage device).

Computer system 300 can indicate corrective actions to take by selectingan instruction from a list of instructions based on monitor wafer coppercontent measurements and displaying the instruction on, for example,display device 370. The instructions would correlate to the correctiveactions listed supra and would be (for example) selected from the groupconsisting of (i) an instruction to shut down the tank of the processingtool containing the solution, (ii) an instruction to limit types ofproduct wafers allowed in the tank, (iii) an instruction to restrictfabrication levels of product wafers allowed in the tank, (iv) aninstruction to limit a number of product wafers that can be processedbefore shutting down the tank, and (v) an instruction to shut down thetank, drain the solution from the tank, clean the tank, and refill thetank with fresh solution.

Thus the present invention discloses a process for supporting computerinfrastructure, integrating, hosting, maintaining, and deployingcomputer-readable code into the computer system 300, wherein the code incombination with the computer system 300 is capable of performing amethod for monitoring copper contamination in wet processing tanks ofintegrated circuit fabrication facilities.

Thus, the embodiments of the present invention provide methods andsystems for monitoring copper contamination of solutions in wetprocessing tanks in integrated circuit manufacturing facilities.

The description of the embodiments of the present invention is givenabove for the understanding of the present invention. It will beunderstood that the invention is not limited to the particularembodiments described herein, but is capable of various modifications,rearrangements and substitutions as will now become apparent to thoseskilled in the art without departing from the scope of the invention.For example, the present invention may be used to monitor sprayprocessing tools where the solution is continuously collected andreused. Therefore, it is intended that the following claims cover allsuch modifications and changes as fall within the true spirit and scopeof the invention.

1. A method, comprising: (a) ion-implanting an N-type dopant into aregion of single-crystal silicon substrate, said region abutting a topsurface of said substrate; (b) activating said N-type dopant byannealing said substrate at a temperature of 500° C. or higher in aninert atmosphere; (c) submerging, for a present duration of time, saidsubstrate into an aqueous solution, said aqueous solution to bemonitored for copper contamination; and (d) determining an amount ofcopper adsorbed from said aqueous solution by said region of saidsubstrate.
 2. The method of claim 1, further including: before (a),forming a thermal oxide layer on said top surface of said substrate. 3.The method of claim 2, further including: between (c) and (d), removingsaid thermal oxide layer.
 4. The method of claim 1, further including:before (a), cleaning said top surface of said substrate.
 5. The methodof claim 1, further including: before (a), selecting an ion implantationN-type dopant dose and energy to repeatably provide a copper measuringsensitivity of said region of said substrate in the range of copperconcentrations expected to be found in said solution.
 6. The method ofclaim 1, further including: (e) determining a copper concentration ofsaid solution based on said amount of copper found in said region ofsaid substrate.
 7. The method of claim 6, wherein (e) includes:determining said copper concentration of said solution based on anempirically derived curve, table or formula derived from measuringamounts of copper in monitor wafers submerged, for said present durationof time, in respective aqueous solutions having known and differentcopper concentrations.
 8. The method of claim 1, further including:using said solution in a fabrication process used to fabricateintegrated circuits.
 9. The method of claim 1, further including:containing said solution in a processing tank of a wet processing toolused in said fabrication process used to fabricate integrated circuits.10. The method of claim 1, wherein said solution to be monitored inselected from the group consisting of aqueous wafer cleaning solutions,aqueous wafer etching solutions, aqueous photoresist developingsolutions and aqueous photoresist removal solutions.
 11. The method ofclaim 1, wherein said solution to be monitored contains fluorine ions.12. The method of claim 1, wherein after (c), a concentration of saidN-type dopant in said region is between about 5 E19 atm/cm³ and about 1E22 atm/cm³.
 13. The method of claim 1, wherein said determining saidamount of copper in said region of said substrate includes performingTotal Internal Reflected X-Ray Fluorescence, Secondary Ion MassSpectroscopy, Time of Flight SIMS, Energy Dispersive X-Ray Fluorescence,Auger Spectroscopy or X-Ray Photo-electron Spectroscopy.
 14. The methodof claim 1, further including: based on said determining an amount ofcopper in said region of said substrate, (e) implementing a correctiveaction selected from the group consisting of shutting down a tank of awet processing tool used in the fabrication of integrated circuitscontaining said solution, limiting types of product wafers allowed insaid tank, restricting fabrication levels of product wafers allowed insaid tank, limiting a number of product wafers that can be processedbefore shutting down said tank, and shutting down said tank, drainingsaid solution from said tank, cleaning said tank, and refilling saidtank with fresh solution.
 15. The method of claim 1, wherein saiddetermining said amount of copper in said region of said substrateincludes performing Secondary Ion Mass Spectroscopy, Time of FlightSIMS, Energy Dispersive X-Ray Fluorescence, Auger Spectroscopy or X-RayPhoto-electron Spectroscopy.